Van der Waals Layered Mineral Getchellite with Anisotropic Linear and Nonlinear Optical Responses

Abstract

Ultrathin ternary 2D materials have recently gained significant attention in the context of tailoring physical properties of materials via stoichiometric variation, which are crucial to many applications in optoelectronics, thermoelectrics, and nanophotonics. Herein, sulfide mineral getchellite is identified as a new type of ternary layered material and large‐area getchellite thin flakes are prepared through mechanical exfoliation. The highly anisotropic linear and nonlinear optical responses of getchellite thin flakes facilitated by the reduced in‐plane crystal symmetry are reported, including anisotropic Raman scattering, wavelength‐dependent linear dichroism transition, and anisotropic third‐harmonic generation (THG). Furthermore, the third‐order nonlinear susceptibility for getchellite crystal is retrieved from the thickness‐dependent THG emission. The demonstrated strong anisotropic linear and nonlinear optical properties of van der Waals layered getchellite will have implications for future technological innovations in photodetectors, optical sensors, nonlinear optical signal processors, and other on‐chip photonic device prototypes.

Polarization-sensitive optical responses from natural layered hydrated sodium sulfosalt gerstleyite

“…Such linear dichroism transition can be understood in the context of singularities in the joint density of states induced strong localization of the absorption peaks along two principal crystal directions in the energy band at the specific photon energies 19 , 28 . Such interesting observations have also been reported in several other 2D crystals such as palladium diselenide PdSe 2 , BaTiS 3 and getchellite 18 , 19 , 28 . Nevertheless, further studies correlating the gerstleyite crystal band structure and the associated optical transitions are essential to obtain insight about this interesting phenomenon.…”

“…In our case, gerstleyite crystal belongs to the monoclinic crystal family, which can support both A g and B g modes. The corresponding Raman tensor for different A g and B g modes can be written as 18 where a , b , c , d , e , and f are the amplitudes of Raman tensor elements with the associated complex phase factors. Taken into consideration of and in parallel polarization configuration, the resultant Raman intensity for A g and B g modes can be expressed as …”

“…From literature, the real part of the refractive index of gerstleyite crystal is around 2.01 58 . Thus, considering all the experimental parameters into account, the third-order nonlinear susceptibility magnitude of for gerstleyite crystal is estimated as 1.81 × 10 –20 m 2 /V 2 , which has the same order of magnitude as the recently explored multi-element anisotropic nonlinear vdW layered materials for example franckeite (1.87 × 10 –19 m 2 /V 2 ) 26 , cylindrite (3.06 × 10 –19 m 2 /V 2 ) 27 , teallite (3.49 × 10 –19 m 2 /V 2 ) 29 , gillulyite (2.05 × 10 –20 m 2 /V 2 ) 30 , getchellite (2.89 × 10 –20 m 2 /V 2 ) 18 , and nagyágite (1.49 × 10 –20 m 2 /V 2 ) 59 .…”

“…Noticeably, these applications are primarily realized on traditional mono- and binary-element vdW layered materials such as graphene, black phosphorous, GeAs, ReS 2 and transition metal dichalcogenides, therefore the material-associated inherent limitations such as elementary crystal structures, simple chemical compositions, material-dependent electronic and optical responses make the applications relatively monotonous and further confine their adaptability 10 – 13 . To address these limitations of mono- and binary-element materials, multi-element vdW layered materials 14 , 15 facilitate an alternative and versatile testbed for realizing innovative electronic, photonic and optoelectronic applications 10 – 12 , according to their complex crystal structures, stoichiometric variations, and exceptional physical and chemical properties such as high charge carrier mobility 10 , 16 , favorable band structure 17 , unique phonon vibrations 11 , 17 , linear dichroism transition 18 , 19 , and robust air stability. In recent years, complex vdW layered materials have established their prospects via their engagement in many important applications.…”

“…Recently, complex multi-element vdW layered materials have attracted vast attention in the context of anisotropic linear and nonlinear optical responses 18 , 26 – 30 . Since the anisotropic optical responses are prominently material specific, it is obligatory to explore more new types of multi-element vdW materials for thriving their unique physical properties and increased adaptability and versatility in more applications.…”